Isotyping immunoglobulins using accurate molecular mass

ABSTRACT

This document relates to methods for detecting and quantifying heavy and light chains of immunoglobulin using mass spectrometry techniques.

CROSS-REFERENCE

This application is a continuation of U.S. application Ser. No.15/301,633, filed Oct. 3, 2016, which is a National Stage Applicationunder 35 U.S.C. § 371 of International Application No.PCT/US2015/024379, filed Apr. 3, 2015, which claims the benefit of U.S.Provisional Application No. 61/975,524, filed Apr. 4, 2014, which arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

This document relates to methods for detecting and quantifying heavy andlight chains of immunoglobulin using mass spectrometry techniques.

BACKGROUND

Human immunoglobulins contain two identical heavy chain polypeptides(each about 54 kilodaltons in MW) and two identical light chainpolypeptides (each about 24 kilodaltons in molecular weight) which arebound together by disulfide bonds. Each light chain and each heavy chaininclude a constant region and a variable region. The variable region islocated on the N-terminal portion of each chain and the constant regionis located on the C-terminal portion of each chain. The constant regionsof the light chains and heavy chains have different amino acidsequences, and can be used to identify the isotype of the heavy or lightchain. In humans, there are two different isotypes of light chainpolypeptides referred to as either kappa or lambda; and five differentisotypes of heavy chain polypeptides referred to as gamma (IgG), alpha(IgA), mu (IgM), epsilon (IgE), and delta (IgD).

Clinical laboratories currently quantify and isotype serumimmunoglobulins using a combination of protein gel electrophoresis (PEL)and imunogixation (IFE). For a normal healthy individual theelectrophoretic pattern observed is an evenly dispersed stainingpattern. This pattern reflects the polyclonal background produced by thelarge number (approximately 6.3×10⁶ heavy chains and 3.5×10⁵ lightchains) of immunoglobulin heavy chains and light chains generated as afunction of somatic hypermutation. In certain diseases, such aspolyclonal gammopathy, there is an increase in the total amount ofimmunoglobulins in the bloodstream or in urine relative to a healthyindividual. In other diseases, such as multiple myeloma, this increasein the amount immunoglobulins is due to a monoclonal immunoglobulin inthe bloodstream. If high levels of the monoclonal immunoglobulin aredetected, additional tests are performed to determine the isotypes ofthe heavy and light chains of the monoclonal immunoglobulin.

Likewise, clinical laboratories now assess cerebral spinal fluid (CSF)with isoelectric focusing gel electrophoresis followed by IgGimmunoblotting (IgG IEF) to detect IgG clones in CSF as compared toserum. See e.g., Fortini A S, Sanders E L, Weinshenker B G, Katzmann JA. Am J Clin Pathol. 2003 November; 120(5):672-5. One or more CSF bands(i.e. oligoclonal bands; OCB) that are not present in serum suggest thatB cell clones are actively producing IgG as part of an inflammatoryresponse in the CNS. Detection of OCB is a sensitive method for CSFinflammatory diseases, and in MS 95% of patients have IgG CSF-specificOCB. Awad A, Hemmer B, Hartung H P, Kieseier B, Bennett J L, Stuve O. JNeuroimmunol. 2010 Feb. 26; 219(1-2):1-7.

SUMMARY

Provided herein are methods of detecting immunoglobulin light chains,immunoglobulin heavy chains, or mixtures thereof in a sample. The methodincludes providing a sample comprising an immunoglobulin light chain, animmunoglobulin heavy chain, or mixtures thereof; immunopurifying,diluting, and/or concentrating the sample; and subjecting the sample toa mass spectrometry technique to obtain a mass spectrum of the sample.

In some embodiments, the immunopurifying includes using an antibodyselected from the group consisting of an anti-human IgG antibody, ananti-human IgA antibody, an anti-human IgM antibody, an anti-human IgDantibody, an anti-human IgE antibody, an anti-human kappa antibody, ananti-human lambda antibody, and combinations thereof. The antibody canbe a non-human antibody. In some embodiments, the non-human antibody isat least one of a camelid antibody, a cartilaginous fish antibody,llama, sheep, goat, or a mouse antibody.

In some embodiments, the antibody for immunopurification is a singledomain antibody fragment. The single domain antibody fragment (SDAF) canbe selected from the group consisting of an anti-human IgG SDAF, ananti-human IgA SDAF, an anti-human IgM SDAF, an anti-human IgD SDAF, ananti-human IgE SDAF, an anti-human kappa SDAF, an anti-human lambdaSDAF, and combinations thereof. In some embodiments, the single domainantibody fragment is derived from a camelid antibody, a cartilaginousfish antibody, llama, a mouse antibody, sheep, goat, or a humanantibody.

The single domain antibody fragment can be selected such that the massspectrum generated in step c) for the single domain antibody fragmentdoes not overlap with the mass spectrum generated in step c) for theimmunoglobulin light chain or immunoglobulin heavy chain. In someembodiments, the single domain antibody fragment is selected such thatthe single domain antibody fragment generates a signal of about 12,500to about 15,000 m/z in step c) with a single charge.

In some embodiments, the immunoglobulin light chains are decoupled fromthe immunoglobulin heavy chains prior to subjecting the sample to a massspectrometry technique to obtain a mass spectrum of the sample. Theimmunoglobulin light chains can be decoupled by cleavage of thedisulfide bonds between the light and heavy chains. For example, thedisulfide bonds can be cleaved using a reducing agent capable ofreducing the disulfide bonds. In some embodiments, the reducing agent isselected from the group consisting of DTT (2,3dihydroxybutane-1,4-dithiol), DTE (2,3 dihydroxybutane-1,4-dithiol),thioglycolate, cysteine, sulfites, bisulfites, sulfides, bisulfides,TCEP (tris(2-carboxyethyl)phosphine), and salt forms thereof.

In some embodiments, the method further includes determining the ratioof kappa and lambda immunoglobulin light chains in the sample after stepsubjecting the sample to a mass spectrometry technique to obtain a massspectrum of the sample.

In some embodiments, the light chains are not fragmented during the massspectrometry technique.

The sample can be a biological sample. For example, the biologicalsample can be a whole blood sample, a serum sample, a plasma sample, aurine sample, or a cerebral spinal fluid sample. The biological samplecan be a mammalian biological sample. In some embodiments, the mammalianbiological sample is a human biological sample.

In some embodiments, the mass spectrometry technique includes a liquidchromatography-mass spectrometry (LC-MS) technique. For example, themass spectrometry technique can include a microflow liquidchromatography electrospray ionization coupled to a quadrupoletime-of-flight mass spectrometry (microLC-ESI-Q-TOF MS) technique. Insome embodiments, the LC-MS technique includes the use of positive ionmode.

In some embodiments, the mass spectrometry technique includes a matrixassisted laser adsorption ionization-time of flight mass spectrometry(MALDI-TOF MS) technique.

In some embodiments, the sample including immunoglobulin light chains,immunoglobulin heavy chains, or mixtures thereof is analyzed as a singlefraction in a single analysis.

The method can further include determining the pairing of immunoglobulinheavy chains and immunoglobulin light chains in the sample. In someembodiments, the method further includes isotyping one or more of theimmunoglobulin light chains in the sample. In some embodiments, themethod further includes isotyping one or more of the immunoglobulinheavy chains in the sample. In some embodiments, the method furtherincludes isotyping one or more of the immunoglobulin light chains andimmunoglobulin heavy chains in the sample. In some embodiments, themethod further includes identifying one or more of the immunoglobulinlight chains and immunoglobulin heavy chains. In some embodiments, themethod further includes quantitating the amount of one or more of theimmunoglobulin light chains and immunoglobulin heavy chains in thesample.

In some embodiments, the method further includes identifying theM-protein in the sample. The method can further include quantifying theM-protein in the sample. In some embodiments, the method furtherincludes identifying determining the pairing of immunoglobulin heavychains and immunoglobulin light chains in the M-protein in the sample.

In some embodiments, the ratio of the kappa and lambda light chains isdetermined by measuring the peak area of one or more multiply chargedion peaks corresponding to each chain. The kappa and lambda light chainscan be quantified by converting the peak area of the multiply chargedion peaks to a molecular mass. In some embodiments, a surrogate internalstandard can be used such that the mass of the internal standard dosenot overlap with the mass of the protein being quantitated.

Accordingly, provided herein is a method for detecting immunoglobulinlight chains, immunoglobulin heavy chains, or mixtures thereof in asample. The method includes (a) providing a sample comprising animmunoglobulin light chain, an immunoglobulin heavy chain, or mixturesthereof; (b) immunopurifying the sample utilizing a single domainantibody fragment; (c) decoupling light chain immunoglobulins from heavychain immunoglobulins; and (d) subjecting the immunopurified sample to amass spectrometry technique to obtain a mass spectrum of the sample; (e)determining one or more of (i) the ratio of kappa and lambdaimmunoglobulin light chains; (ii) the isotype of the immunoglobulinlight chains; (iii) the isotype of the immunoglobulin heavy chains; (iv)the isotype of one or more of the immunoglobulin light chains andimmunoglobulin heavy chains; and (v) the quantitative amount of one ormore of the immunoglobulin light chains and immunoglobulin heavy chainsin the sample. The mass spectrometry technique is chosen from the groupconsisting of (i) liquid chromatography electrospray ionization coupledto mass analyzer (quadrupole, time of flight or orbitrap) (ii) amicroflow liquid chromatography electrospray ionization coupled to aquadrupole time-of-flight mass spectrometry (microLC-ESI-Q-TOF MS orMS/MS) technique and (iii) a matrix assisted laser adsorptionionization-time of flight mass spectrometry (MALDI-TOF MS or MS/MS)technique.

Also, provided herein is a method for analyzing immunoglobulin lightchains, immunoglobulin heavy chains, or mixtures thereof in a sample.The method includes (a) providing a sample comprising an immunoglobulinlight chain, an immunoglobulin heavy chain, or mixtures thereof; (b)immunopurifying the sample utilizing a single domain antibody fragment;(c) optionally decoupling the light chain immunoglobulins from the heavychain immunoglobulins, wherein one or more of the immunoglobulin lightchains or immunoglobulin heavy chains are derived from an M-protein; (d)subjecting the immunopurified sample to a mass spectrometry technique toobtain a mass spectrum of the sample; and (e) determining one or more of(i) the identity of the M-protein; (ii) the quantity of the M-protein;(iii) the pairing of immunoglobulin heavy chains and immunoglobulinlight chains of the M-protein; and (iv) the quantitative amount of oneor more of the immunoglobulin light chains, immunoglobulin heavy chains,and M-protein in the sample. The mass spectrometry technique is chosenfrom the group consisting of (i) liquid chromatography electrosprayionization coupled to mass analyzer (quadrupole, time of flight ororbitrap) (ii) a microflow liquid chromatography electrospray ionizationcoupled to a quadrupole time-of-flight mass spectrometry(microLC-ESI-Q-TOF MS or MS/MS) technique and (iii) a matrix assistedlaser adsorption ionization-time of flight mass spectrometry (MALDI-TOFMS or MS/MS) technique. Further, provided herein is a method fordiagnosing a disorder in a subject. The method includes providing asample from the subject comprising an immunoglobulin light chain, animmunoglobulin heavy chain, or mixtures thereof; immunopurifying thesample; subjecting the immunopurified sample to a mass spectrometrytechnique to obtain a mass spectrum of the sample; determining the ratioof the kappa and lambda immunoglobulin light chains in the sample; andcomparing the ratio to a reference value.

The disorder can be selected from the group consisting of an autoimmunedisorder, an inflammatory disorder, an infectious disorder, and apolyclonal gammopathy. In some embodiments, the disorder is selectedfrom the group consisting of plasma cell dyscrasias,hypergammaglobulinemia, multiple sclerosis, neuromyelitus optica,neurosarcoidosis, subacute sclerosing panencephalitis, ANCA associatedvasculitis, paraneoplastic syndromes, celiac disease, Sjogrens Syndrome,rheumatoid arthritis, and Guillian-Barrre Syndrome. ANCA associatedvasculitis includes three systemic autoimmune small vessel vasculitissyndromes that are associated with antineutrophil cytoplasmicautoantibodies (ANCAs). ANCA associated vasculitis includes microscopicpolyangiitis (MPA), granulomatosis with polyangiitis (GPA), formerlyknown as Wegener's granulomatosis, and eosinophilic granulomatosis withpolyangiitis (EGPA), formerly known as Churg-Strauss syndrome. When thedisorder is hypergammaglobulinemia, in addition to the kappa and lambdaratio, distinct monoclonal light chains can be identified above thepolyclonal background. The method can be performed to confirm theresults of a protein electrophoresis (PEL) or immunofixation test.

Additionally, provided herein is a method of monitoring a treatment of adisorder in a subject, wherein the disorder is associated with anabnormal kappa and lambda immunoglobulin light chain ratio. The methodincludes (a) providing an initial sample from the subject; (b) providingone or more secondary samples from the subject during the treatment,after the treatment, or both; (c) immunopurifying the sample; (d)subjecting the samples to a mass spectrometry technique to obtain a massspectrum of the sample; (e) determining the ratio of the kappa andlambda immunoglobulin light chains in the samples; and (f) comparing theratios from the initial and the one or more secondary samples.

Further, provided herein is a method for quantifying the kappa andlambda immunoglobulin light chains in a sample. The method includes (a)providing a sample comprising one or more immunoglobulin light chains;(b) immunopurifying the samples; (c) subjecting the immunopurifiedsample to a mass spectrometry technique to obtain a mass spectrum of thesamples; (d) identifying the multiply charged ion peaks in the spectrumcorresponding to the kappa and lambda immunoglobulin light chains; and(e) converting the peak area of the identified peaks to a molecular massto quantify the kappa and lambda immunoglobulin light chains in thesample.

Provided herein is a method of diagnosing a disorder in a subject,wherein the disorder is associated with an inflammatory response in thecentral nervous system. The method includes (a) providing a cerebralspinal fluid (CSF) sample comprising one or more immunoglobulins; (b)subjecting the CSF sample to a mass spectrometry technique to obtain amass spectrum of the CSF sample; and (c) identifying a mass peakcorresponding to one or more immunoglobulin light chains in the CSFsample.

In some embodiments, the immunoglobulin light chains are decoupled bycleavage of the disulfide bonds between the light and heavy chains. Thedisulfide bonds can be cleaved using a reducing agent capable ofreducing the disulfide bonds. For example, the reducing agent can beselected from the group consisting of: DTT (2,3dihydroxybutane-1,4-dithiol), DTE (2,3 dihydroxybutane-1,4-dithiol),thioglycolate, cysteine, sulfites, bisulfites, sulfides, bisulfides,TCEP (tris(2-carboxyethyl)phosphine), and salt forms thereof.

In some embodiments, prior to subjecting the CSF sample to a massspectrometry technique to obtain a mass spectrum of the CSF sample, theCSF sample is diluted. For example, the CSF sample can be diluted withbuffer.

In some embodiments, the mass spectrometry technique includes a liquidchromatography-mass spectrometry (LC-MS) technique. The massspectrometry technique can include a microflow liquid chromatographyelectrospray ionization coupled to a quadrupole time-of-flight massspectrometry (microLC-ESI-Q-TOF MS/MS) technique. The LC-MS techniquecan include the use of positive ion mode.

In some embodiments, the disorder is selected from the group consistingof plasma cell dyscrasias, hypergammaglobulinemia, multiple sclerosis,neuromyelitus optica, neurosarcoidosis, subacute sclerosingpanencephalitis, ANCA associated vasculitis, paraneoplastic syndromes,celiac disease, Sjogrens Syndrome, rheumatoid arthritis, andGuillian-Barrre Syndrome The method can further include providing aserum sample including one or more immunoglobulins, subjecting the serumsample to a mass spectrometry technique to obtain a mass spectrum of thesample; identifying a mass peak corresponding to one or more lightchains in the serum sample; and comparing (i) the mass peakscorresponding to the one or more light chains in the CSF sample to (ii)the mass peaks corresponding to one or more light chains in the serumsample.

In some embodiments, the serum sample is enriched prior to subjectingthe sample to the mass spectrometry technique.

The presence of one or more peaks in the CSF sample not present in theserum sample can indicate an inflammatory response in the centralnervous system. For example, the one or more peaks in the CSF sample notpresent in the serum sample can include an oligoclonal band (OCB).

Accordingly, provided herein is a method of diagnosing a disorder in asubject, wherein the disorder is associated with an inflammatoryresponse in the central nervous system. The method includes (a)providing a CSF sample comprising one or more immunoglobulins and aserum sample comprising one or more immunoglobulins; (b) subjecting theCSF sample and the serum sample to a mass spectrometry technique toobtain a mass spectrum of the CSF sample and serum sample; (c)identifying a mass peak corresponding to one or more light chains in theCSF sample; (e) identifying a mass peak corresponding to one or morelight chains in the serum sample; and (f) comparing (i) the mass peakscorresponding to the one or more light chains in the CSF sample to (ii)the mass peaks corresponding to one or more light chains in the serumsample.

Also provided herein is a method for monitoring a response to atreatment. The method includes (a) providing an initial CSF sample fromthe subject; (b) providing one or more secondary CSF samples from thesubject during the treatment, after the treatment, or both; (c)immunopurifying the CSF samples; (d) subjecting the immunopurified CSFsamples to a mass spectrometry technique to obtain a mass spectrum ofthe CSF samples; (e) comparing (i) the mass peaks in the initial CSFsample to (ii) the mass peaks in the one or more secondary samples. Theinitial sample can be a baseline sample or a control sample, or, forexample a sample taken from the subject prior to the start of treatment.

Also provided herein are methods of using mass spectrometry methods(e.g., microLC-ESI-Q-TOF MS) for identifying and quantifying the heavyand light chains of immunoglobulins in biological samples. This is due,in part, to the fact that the mass difference of the constant regions ofvarious isotypes of both the heavy and light chains contribute to theobservation of distinct molecular mass profiles for each isotype. Usingimmunoglobulin enriched, DTT reduced, pooled normal human serum as areference, molecular mass profiles for each isotype were established andfound to fit a normal distribution. Moreover, in the case of theimmunoglobulin light chains, the kappa/lambda peak area ratios areanalogous to the kappa/lambda ratios observed using other publishedmethods. In addition, the methods provided herein can be used to monitorkappa and lambda light chain repertoires in serum (e.g., in variousmammalian species). The results shown for subjects withhypergammaglobulinemia and other disorders further highlight theusefulness of the methods provided herein for assessing the relativeabundance of the kappa and lambda light chain repertoires in subjectswith abnormal immunoglobulin levels. This finding is significant sinceit demonstrates that an abnormal polyclonal kappa/lambda ratio in serumcan be identified quickly and inexpensively using the molecular massprofiling methods described herein. In addition, detection and isotypingthe immunoglobulin heavy chains can have implications in theidentification and treatment of disorders such as Multiple Myeloma.

Accordingly, provided herein is a method for determining a ratio ofkappa and lambda immunoglobulin light chains in a sample, the methodcomprising: providing a sample comprising one or more immunoglobulinlight chains; subjecting the sample to a mass spectrometry technique toobtain a mass spectrum of the sample; and determining the ratio of thekappa and lambda immunoglobulin light chains in the sample.

In some embodiments, the immunoglobulin light chains are decoupled fromthe immunoglobulin heavy chains prior to subjecting the sample to a massspectrometry technique. For example, the immunoglobulin light chains canbe decoupled by cleavage (e.g., reduction) of the disulfide bondsbetween the light and heavy chains. Any suitable reducing agent can beused, for example, the reducing agent can be selected from the groupconsisting of: DTT (2,3 dihydroxybutane-1,4-dithiol), DTE (2,3dihydroxybutane-1,4-dithiol), thioglycolate, cysteine, sulfites,bisulfites, sulfides, bisulfides, TCEP (tris(2-carboxyethyl)phosphine),and salt forms thereof. In some embodiments, the immunoglobulins in thesample are enriched in the sample prior to subjecting the sample to amass spectrometry technique.

In some embodiments, the light chains are not fragmented during the massspectrometry technique.

A sample can include a biological sample such as a whole blood sample,serum sample, plasma sample, or urine sample. In some embodiments, thebiological sample is a mammalian biological sample (e.g., a humanbiological sample).

The mass spectrometry techniques used herein can include a liquidchromatography-mass spectrometry (LC-MS) technique. In some embodiments,the mass spectrometry technique comprises a microflow liquidchromatography electrospray ionization coupled to a quadrupoletime-of-flight mass spectrometry (microLC-ESI-Q-TOF MS) technique. Insome embodiments, the LC-MS technique comprises the use of positive ionmode.

In some cases, the ratio of the kappa and lambda light chains isdetermined by measuring the peak area of one or more multiply chargedion peaks corresponding to each chain. The peak areas of the multiplycharged ion peaks can be converted to a molecular mass. In someembodiments, the molecular mass measurements can be used to quantify thekappa and lambda light chains.

In some embodiments, a method for determining a ratio of kappa andlambda immunoglobulin light chains in a sample comprises: providing asample enriched in one or more immunoglobulins; decoupling light chainimmunoglobulins from heavy chain immunoglobulins in the immunoglobulinsin the sample to generate a decoupled immunoglobulin sample; subjectingthe sample to a microflow liquid chromatography electrospray ionizationcoupled to a quadrupole time-of-flight mass spectrometry technique toobtain a mass spectrum of the sample; and determining the ratio of thekappa and lambda immunoglobulin light chains in the sample.

Also provided herein is a method for diagnosing a disorder in a subject,the method comprising: providing a sample from the subject comprisingone or more immunoglobulin light chains; subjecting the sample to a massspectrometry technique to obtain a mass spectrum of the sample;determining the ratio of the kappa and lambda immunoglobulin lightchains in the sample; and comparing the ratio to a reference value.Exemplary disorders that can be diagnosed using these methods include anautoimmune disorder, an inflammatory disorder, an infectious disorder,and a polyclonal gammopathy. In some embodiments, the disorder ishypergammaglobulinemia and in addition to the kappa and lambda ratio,distinct monoclonal light chains can be identified above the polyclonalbackground. In some embodiments, the methods described herein areperformed to confirm the results of a protein electrophoresis (PEL) orimmunofixation test.

Further provided herein is a method of monitoring a treatment of adisorder in a subject, wherein the disorder is associated with anabnormal kappa and lambda immunoglobulin light chain ratio, the methodcomprising: providing a first sample of the subject before thetreatment; providing a second sample of the subject during or after thetreatment; subjecting the samples to a mass spectrometry technique toobtain a mass spectrum of the sample; determining the ratio of the kappaand lambda immunoglobulin light chains in the samples; and comparing theratios from the first and second samples.

The methods provided herein can also be used to quantifying the kappaand lambda immunoglobulin light chains in a sample. In some embodiments,the method comprises: providing a sample comprising one or moreimmunoglobulin light chains; subjecting the sample to a massspectrometry technique to obtain a mass spectrum of the sample;identifying the multiply charged ion peaks in the spectrum correspondingto the kappa and lambda immunoglobulin light chains; and converting thepeak area of the identified peaks to a molecular mass to quantify thekappa and lambda immunoglobulin light chains in the sample.

Provided herein is a method for diagnosing hypergammaglobulinemia in asubject, the method comprising: providing a sample from the subjectcomprising one or more immunoglobulin light chains; subjecting thesample to a mass spectrometry technique to obtain a mass spectrum of thesample; determining the total amount of the kappa and lambdaimmunoglobulin light chains in the sample; and comparing the amount inthe sample to a reference value, wherein a higher than reference totalamount indicates that the subject has hypergammaglobulinemia. In someembodiments, the total amount of the kappa and lambda immunoglobulinlight chains in the sample is at least 2-fold higher than the referencevalue.

The methods described herein are also useful for determining the isotypeof one or more immunoglobulin heavy chains in a sample. In someembodiments, the method comprises: providing a sample comprising one ormore immunoglobulin heavy chains; subjecting the sample to a massspectrometry technique to obtain a mass spectrum of the sample; andidentifying the mass peaks corresponding to one or more isotypes of animmunoglobulin heavy chain in the sample.

Also provided herein is a method for determining the isotype of one ormore immunoglobulin light chains in a sample, the method comprising:providing a sample comprising one or more immunoglobulin light chains;subjecting the sample to a mass spectrometry technique to obtain a massspectrum of the sample; and identifying the mass peaks corresponding toone or more isotypes of an immunoglobulin light chain in the sample.

The method provided herein can be used to diagnose a disorder in asubject, wherein the disorder is associated with one or more heavy chainimmunoglobulin isotypes, the method comprising: providing a samplecomprising one or more immunoglobulin heavy chains; subjecting thesample to a mass spectrometry technique to obtain a mass spectrum of thesample; and identifying the mass peaks corresponding to one or moreisotypes of an immunoglobulin heavy chain in the sample. Exemplarydisorders include monoclonal gammopathy of underdetermined significance(MGUS), light chain deposition disease, amyloidosis, multiple myeloma,heavy chain deposition disease, and POEMS syndrome.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this description belongs. Methods and materials aredescribed herein for use in the present invention; other, suitablemethods and materials known in the art can also be used. The materials,methods, and examples are illustrative only and not intended to belimiting. All publications, patent applications, patents, and otherreferences mentioned herein are incorporated by reference in theirentirety. In case of conflict, the present specification, includingdefinitions, will control. Other features and advantages of theinvention will be apparent from the following detailed description andfigures, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates the expected theoretical molecular mass profiles thatwould be observed for each of the three regions (V, J, and C) for bothkappa and lambda light chains.

FIG. 2 shows the amino acid sequences for the constant regions for kappaand lambda light chains along with the molecular mass difference betweenthe kappa constant region and the average mass of the four lambdaconstant regions.

FIG. 3 shows the histograms constructed for kappa and lambda using thecalculated molecular masses displayed in 100 Da bin widths.

FIG. 4 shows a total ion chromatogram obtained from the injection of 2μL melon gel purified and DTT reduced normal pooled serum analyzed bymicroLC-ESI-Q-TOF MS.

FIG. 5 shows the mass spectrum obtained by summing the spectra collecteda 1 minute window with the charge state of the expected polyclonal kappalight chains shown next to the highlighted vertical line.

FIG. 6 provides the deconvoluted mass spectrum of FIG. 5 transformed tomolecular mass and showing the kappa and lambda polyclonal molecularmass profile.

FIG. 7 shows the results comparing the deconvoluted molecular massprofiles for normal pooled serum (top), IgG kappa purified normal pooledserum (middle), and IgG lambda purified normal pooled serum (bottom).

FIG. 8 provides the results for pooled serum samples derived from sheep,goats, cows, and horses.

FIG. 9 shows the +11 charge state kappa and lambda light chain ionsobserved from serum taken from a patient with hypergammaglobulinemia(upper trace) compared to a normal control serum (lower trace).

FIG. 10 shows the +11 charge state ions observed from normal controlserum (top), a patient with a chronic inflammatory response of unknownorigin (middle), and a patient with Sjögren's syndrome an autoimmunedisorder involving the salivary and lacrimal glands (bottom).

FIG. 11 shows the response observed in the light chain mass region for aserum sample spiked with the monoclonal recombinant therapeutic antibodyHUMIRA® (adalimumab) which has a kappa light chain and an IgG heavychain.

FIG. 12 shows the response observed in the light chain mass region for aserum sample from a patient with a known lambda monoclonal free lightchain and who had also been treated with the monoclonal recombinanttherapeutic antibody REMICADE® (infliximab) which has a kappa lightchain and an IgG heavy chain.

FIG. 13 shows the response observed in the heavy chain mass region for aserum sample spiked with the monoclonal recombinant therapeutic antibodyHUMIRA® (adalimumab) which has a kappa light chain and an IgG heavychain.

FIG. 14 is a flow chart of an embodiment of the methods provided herein.

FIG. 15 shows the response observed in the light chain mass region for aserum sample from a patient with HIV infection.

FIG. 16 illustrates the steps in the sample preparation for a gel basedmethod (top) and a mass spectrometry based method (bottom) as providedherein.

FIG. 17 illustrates mass spectra from a patient negative for CSFspecific monoclonal immunoglobulins by IgG IEF analyzed by a massspectrometry based method (bottom), as provided herein.

FIG. 18 illustrates mass spectra from a patient with matching CSF andserum monoclonal immunoglobulins (i.e. a negative patient) by IgG IEFanalyzed by a mass spectrometry based method, as provided herein.

FIG. 19 illustrates mass spectra from a patient positive for CSFspecific monoclonal immunoglobulins by IgG IEF analyzed by a massspectrometry based method, as provided herein.

FIG. 20 illustrates mass spectra from a patient positive for CSFspecific monoclonal immunoglobulins by IgG IEF analyzed by a massspectrometry based method, as provided herein.

FIG. 21 illustrates the +17 charge state kappa light chains from apatient CSF sample positive for OCB that was spiked with a kappa lightchain standard then analyzed by a mass spectrometry based method, asprovided herein. The blue trace is the 1.5 μg/mL spike, the pink traceis the 3 μg/mL spike, the orange trace is the 6 μg/mL spike, and thegreen trace is the 12 μg/mL spike.

DETAILED DESCRIPTION

The amino acid sequence of a human immunoglobulin light chain consistsof three regions: the N-terminal V region (approximately 107 amino acidsfor kappa and 110 amino acids for lambda), the J region (12 aminoacids), and the C-terminal C region (106 amino acids). Each region istranslated from a specific set of genes expressed only in B cells whichmake and secrete light chains either as part of an intact immunoglobulinor as a free light chain. B-cells are also able to randomly mutate V andJ region genes for light chains through the process of somatichypermutation resulting in a large number of different gene combinations(approximately 1.3×10³ for kappa alone) (see, e.g., Lefranc, M P. ColdSpring Harb Protoc 2011; 2011:595-603). Since the light chain V and Jregion gene sequences are created randomly, the Central Limit Theorem(Mukhopadhyay, N and Chattopadhyay, B. Sequential Anal 2012; 31:265-77)predicts that the amino acid sequence of the expressed light chainrepertoire should have a normally distributed molecular mass profile.

FIG. 1 presents an example of the expected theoretical molecular massprofiles that would be observed for each of the three regions (V, J, andC) for both the kappa and lambda light chains. The profiles under the Vand J regions show the predicted normal distribution of the molecularmass profiles of the translated regions while the profiles under the Cregions show single bars. Since the kappa constant region has only oneconserved amino acid sequence it is represented by a single molecularmass bar while the profile under the C region for lambda shows fourdifferent bars, each representing the four different lambda constantregion molecular masses L1, L2, L3, and L7 (McBride, O W et al. J ExpMed 1982; 155:1480-90). FIG. 2 shows the amino acid sequences for theconstant regions for kappa and lambda light chains along with themolecular mass difference between the kappa constant region and theaverage mass of the four lambda constant regions. Assuming that themolecular masses of the V and J region amino acid sequences follow anormal distribution, then the difference between μ for kappa and μ forlambda from their molecular mass profiles should differ by the massdifference of the constant regions (approximately 363.55 Da). Using alight chain gene sequence database containing the entire V and J regionsfor 1087 kappa and 735 lambda light chain sequences the molecular massof the kappa and lambda light chains was calculated. The nucleotidesequence information for each VJ region was converted to the amino acidsequence and then converted to molecular mass. The VJ region molecularmass was then added to the molecular mass of the corresponding kappa orlambda constant region. FIG. 3 shows the histograms constructed forkappa and lambda using the calculated molecular masses displayed in 100Da bin widths. The mean molecular mass for kappa was found to be23,373.41 Da while the mean molecular mass for lambda was found to be22,845.24 Da (mean indicated by vertical red dashed lines). Thistranslates into a difference of 528.17 Da between kappa and lambda lightchains which is greater than the difference of 363.55 Da between themolecular masses of the kappa and lambda constant regions alone. Thisdifference is likely due to the contribution in mass from the frameworkregions (FR) within the V regions which do not undergo completerandomization compared to the complimentary determining regions (CDR)within the V regions.

As with the immunoglobulin light chains, the heavy chains include avariable and a contact region. Using known sequences selectedimmunoglobulin heavy chains (i.e., IgA, IgG, and IgM), the variableregion gene sequences were converted to their respective amino acidsequence and then converted to a molecular mass. These masses were thenadded to the known constant regions molecular masses for IgA, IgG, andIgM. A set of possible molecular mass bins were made at 200 Daincrements and the numbers of clones matching the mass for each bin wererecorded. A smoothed histogram plot of the number of clones in each bin(y-axis) vs. molecular mass of each bin (x-axis) is shown in FIG. 2where the red line (first and third peaks from the left)=IgA, the blueline (second and fourth peaks form the left)=IgG, and the green line(fifth and sixth peaks from the left)=IgM. The plot demonstrates thatthere exists a gap in the molecular mass of each of the different heavychain isotypes analogous to the difference in mass between kappa andlambda light chains. The average known molecular mass of the constantregions for the Ig isotypes are:

-   -   IgA, 2 subclasses, Average Molecular Mass=37,090 Da    -   IgG, 4 subclasses, Average Molecular Mass=37,308 Da    -   IgM, 1 class, Molecular Mass=49,307 Da

The observed molecular mass for each of the immunoglobulin isotypes willbe shifted due to the addition of N-linked and/or O-linkedglycosylation. This post translational modification is a natural processperformed by the B cell but the extent of the glycosylation added by thecell is different for each Ig isotype and therefore should give anadditional means of identifying the isotype without performingadditional MS/MS fragmentation. The isotype glycosylation patters are:

-   -   IgA has both O-linked and N-linked glycosylation    -   IgG has only N-linked glycosylation at Aps 297    -   IgM has 5 N-linked glycosylation sites.

The data provided herein shows that the molecular mass distributionsobserved using the methods described herein represent the entirepolyclonal heavy and light chain repertoire present in the serum. Theability to observe the entire immunoglobulin molecular mass distributionis a unique property of the methods provided herein and allows for theuser to record a specific phenotypic immunoglobulin signature for asample.

Using the distinct molecular mass profiles of the various heavy andlight chain isoptypes, a method for using mass spectrometry to identifyand quantitate the heavy and light immunoglobulin chains in a sample hasbeen discovered. For example, provided herein are methods of using thisdifference in molecular masses to identify and quantify the kappa andlambda light chains in samples using mass spectrometry techniques (seeFIG. 14). The speed, sensitivity, resolution, and robustness of massspectrometry makes the present methods superior than PEL, nephelometry,or IFE for isotyping immunoglobulins and allows for comparisons andquantifications of their relative abundance. Such methods are useful fordiagnosing various disorders and for monitoring patients followingtreatment.

Protein electrophoresis can used be to quantitate CSF immunoglobulins inpatients with multiple sclerosis (MS). See e.g., Kabat E A, Moore D H,Landow H. J Clin Invest. 1942 September; 21(5):571-7. Clinicallaboratories now assess CSF with isoelectric focusing gelelectrophoresis followed by IgG immunoblotting (IgG IEF) to detect IgGclones in CSF as compared to serum. See e.g., Fortini A S, Sanders E L,Weinshenker B G, Katzmann J A. Am J Clin Pathol. 2003 November;120(5):672-5. Multiple CSF bands (i.e. oligoclonal bands—OCB) that arenot present in serum suggest that B cell clones are actively producingIgG as part of an inflammatory response in the CNS. Detection of OCB isa sensitive method for CSF inflammatory diseases, and in multiplesclerosis, 95% of patients have IgG CSF-specific OCB. See e.g., Awad A,Hemmer B, Hartung H P, Kieseier B, Bennett J L, Stuve O. J Neuroimmunol.2010 Feb. 26; 219(1-2):1-7. IgG IEF immunoblots are interpreted as; 1)No bands in serum and CSF (Negative); 2) Matching bands in serum and CSF(Negative); 3) Unique bands in serum (Negative); or 4) Unique bands inCSF (Positive). Further, isolated IgG molecules from CSF fluid have beenanalyzed by IEF gels, with the bands subsequently excised and thenanalyzed by MALD-TOF MS. See e.g., Obermeier et al. Nature Medicine.2008 June; 14(6):688-93. Likewise, CSF has been purified from CSF usingSDS-PAGE, with relevant bands excised, trypsinized, and measured withLC-MS. See e.g., Singh et al. Cerebrospinal-fluid-derived ImmunoglobulinG of Different Multiple Sclerosis Patients Shares Mutated Sequences inComplementary Determining Regions. Mol Cell Proteomics. 2013 December;12(12):3924-34.

Using mass spectrometry methods as provided herein, also referred to asmonoclonal immunoglobulin Rapid Accurate Mass Measurement (miRAMM),oligoclonal immunoglobulins can be detected by assessing theirassociated light chains in cerebral spinal fluid (CSF) and serum. Forexample, the findings for 56 paired CSF and serum samples analyzed byIgG IEF and miRAMM were compared. The two methods were in agreement with54 samples having concordant results (22 positive and 34 negative) and 2that were positive by IgG IEF but negative by miRAMM. Furthermore, inaddition to identifying clonal immunoglobulins, the methods providedherein can be used to quantitate the amount of clonal immunoglobulin.

In various embodiments, the methods provided herein exhibit increasedaccuracy of clone matching between serum and CSF as compared to otherknown methodologies. In various embodiments, the methods have a lowersupply costs as compared to immunofixation (IFE) based techniques. Invarious embodiments, the methods can advantageously quantitate one ormore of the CSF clones.

Plasma cells (PCs) reside in the bone marrow and secrete vast quantitiesof high-affinity antigen specific immunoglobulins. In plasma celldyscrasias (PCDs) there is overrepresentation of specific clonal PCssecreting unique M-proteins with defined masses determined by theisotype of the heavy and/or light chain composing the M-protein. TheseM-proteins are thus biomarkers of PCDs. Thus, if there is clinicalsuspicion of a PCD disorder, the patient's serum and urine is typicallytested for the presence of M-proteins (also known as a monoclonalimmunoglobulins). M-proteins are typically detected using a combinationof protein gel electrophoresis (PEL) and immunofixation.

Samples and Sample Preparation

A sample for analysis can be any biological sample, such as a tissue(e.g., adipose, liver, kidney, heart, muscle, bone, or skin tissue) orbiological fluid (e.g., blood, serum, plasma, urine, lachrymal fluid,saliva, or central spinal fluid) sample. The biological sample can befrom a subject that has immunoglobulins, which includes, but is notlimited to, a mammal, e.g. a human, dog, cat, primate, rodent, pig,sheep, cow, and horse. In some embodiments, the biological samplecomprises an exogenous monoclonal immunoglobulin. A sample can also be aman-made reagent, such as a mixture of known composition or a controlsample.

A sample can be treated to remove components that could interfere withthe mass spectrometry technique. A variety of techniques known to thosehaving skill in the art can be used based on the sample type. Solidand/or tissue samples can be ground and extracted to free the analytesof interest from interfering components. In such cases, a sample can becentrifuged, filtered, and/or subjected to chromatographic techniques toremove interfering components (e.g., cells or tissue fragments). In yetother cases, reagents known to precipitate or bind the interferingcomponents can be added. For example, whole blood samples can be treatedusing conventional clotting techniques to remove red and white bloodcells and platelets. A sample can be deproteinized. For example, aplasma sample can have serum proteins precipitated using conventionalreagents such as acetonitrile, KOH, NaOH, or others known to thosehaving ordinary skill in the art, optionally followed by centrifugationof the sample.

Immunoglobulins can be isolated from the samples or enriched (i.e.concentrated) in a sample using standard methods known in the art. Suchmethods include removing one or more non-immunoglobulin contaminantsfrom a sample. In some embodiments, the samples can be enriched orpurified using immunopurification, centrifugation, filtration,ultrafiltration, dialysis, ion exchange chromatography, size exclusionchromatography, protein A/G affinity chromatography, affinitypurification, precipitation, gel electrophoresis, capillaryelectrophoresis, chemical fractionation (e.g., antibody purificationkits, such as Melon Gel Purification), and aptamer techniques. Forexample, the immunoglobulins can be purified by chemical-basedfractionation, e.g., Melon Gel Chromatography (Thermo Scientific), whereMelon Gel resins bind to non-immunoglobulin proteins in a sample andallow immunoglobulins to be collected in the flow-through fraction; orby affinity purification, e.g., by Protein A, Protein G, or Protein Lpurification, where immunoglobulins are bound by those proteins atphysiologic pH and then released from the proteins by lowering the pH.When serum, plasma, or whole blood samples are used, a sample, such as a10-250 μl sample, e.g., a 50 μl, can be directly subjected to Melon Gel,Protein A, Protein G, or Protein L purification. Size exclusionprinciples such as a TurboFlow column can also be employed to separatethe non-immunoglobulin contaminants from a sample. When urine samplesare used, a urine sample can be buffered, e.g., a 50 μl urine sample canbe diluted first with 50 μl of 50 mM ammonium bicarbonate.

In some embodiments, a sample can be subject to immunopurification priorto analysis by mass spectrometry. In some embodiments, the sample can beimmunoglobulin enriched. For example, immunopurification can result inenrichment of one or more immunoglobulins. In some embodiments,immunopurification can separate or enrich immunoglobulin light chains ina sample. In some embodiments, immunopurification can separate or enrichimmunoglobulin heavy chains in a sample. In some embodiments,immunopurification can separate or enrich immunoglobulin kappa lightchains or immunoglobulin lambda light chains in a sample. In someembodiments, immunopurification can separate or enrich IgG, IgA, IgM,IgD, or IgE in a sample. Immunopurification can involve contacting asample containing the desired antigen with an affinity matrix includingan antibody (e.g. single domain antibody fragments) to the antigencovalently attached to a solid phase (e.g., agarose beads). Antigens inthe sample become bound to the affinity matrix through an immunochemicalbond. The affinity matrix is then washed to remove any unbound species.The antigen is then removed from the affinity matrix by altering thechemical composition of a solution in contact with the affinity matrix.The immunopurification may be conducted on a column containing theaffinity matrix, in which case the solution is an eluent or in a batchprocess, in which case the affinity matrix is maintained as a suspensionin the solution.

In some embodiments, single domain antibody fragments (SDAFs) with anaffinity for immunoglobulins can be used in the immunopurificationprocess. SDAFs can be derived from heavy chain antibodies of non-humansources (e.g., camelids), heavy chain antibodies of human sources, andlight chain antibodies of humans. SDAFs possess unique characteristics,such as low molecular weight, high physical-chemical stability, goodwater solubility, and the ability to bind antigens inaccessible toconventional antibodies.

Employing the combination of enrichment using a collection of antibodies(e.g., single domain antibody fragments) with affinity for one or moreof the different immunoglobulin isotypes coupled with rapid generationof mass spectra using MALDI-TOF mass spectrometry, it was discoveredthat identification of monoclonal proteins, quantitation of M-proteins,and identification of one or more of the heavy or light chainimmunoglobulins, including identification of the heavy/light chainisotype pairings. The methods provided herein can generate clinicalinformation equivalent to the four currently used clinical assays fordiagnosis and monitoring PCDs-PEL, total protein quantitation, IFE andHevy Lite (HCL) assays could be accomplished.

In some embodiments, isolation of immunoglobulins can be performed withan entity other than a traditional antibody—which contains both heavyand light chains (such as those used in IFE and various known clinicalimmunoassays). Traditional antibodies contain heavy and/or light chainswith masses that may overlap with the masses of the immunoglobulins inthe sample of interest (e.g., human immunoglobulins). Therefore, theseantibodies may interfere in the mass spectra of the patient'simmunoglobulins. Single domain antibody fragments (SDAFs) may havemasses ranging from 12,500-15,000 Da and, using the methods describedherein, may carry a single charge thus generating a signal in the rangeof 12,500-15,000 m/z, which does not overlap with the signals generatedby human heavy chains or light chains. Also, accurate molecular massalone is not 100% specific in identification of immunoglobulin isotypeas there are m/z regions (23,000-23,200 m/z or 11,500-11,600 m/z) whereimmunoglobulins may be of the kappa or lambda light chain isotype. Thus,in some embodiments, the use of specific isolation of heavy and/or lightchains utilizing SDAFs, coupled with mass identification, results in aspecific and sensitive method for the detection of immunoglobulin heavychains and immunoglobulin light chains.

In various embodiments, the use of single domain antibody fragments maybe used in place of concentrating samples with low concentrations ofimmunoglobulins prior to analysis. In various some embodiments, themethod described herein can replace the need for total proteinmeasurement and protein gel electrophoresis of urine or serum in orderto quantitate specific monoclonal proteins. In various embodiments, themethod can identify all the major types of monoclonal isotypes ofM-proteins with sensitivity exceeding current methods. In variousembodiments, the method is faster, less expensive, less laborious, andautomatable. In various embodiments, the method is advantageous becauseit creates an electronic record as opposed to a gel. In variousembodiments, the method overcomes the shortcoming of previous methods inthat data acquisition can take less than 15 seconds per sample.

In some embodiments, the immunoglobulins, or the heavy and/or lightchains thereof, are substantially isolated. By “substantially isolated”is meant that the immunoglobulins are at least partially orsubstantially separated from the sample from which they were provided.Partial separation can include, for example, a sample enriched in theimmunoglobulins (i.e., the heavy and/or light chains). Substantialseparation can include samples containing at least about 10%, at leastabout 20%, at least about 30%, at least about 40%, at least about 50%,at least about 60%, at least about 70%, at least about 80%, at leastabout 90%, at least about 95%, at least about 97%, or at least about 99%by weight of the immunoglobulin, or the heavy and/or light chainsthereof. Methods for isolating immunoglobulins, such as those describedabove, are routine in the art.

Intact immunoglobulins can be further processed to decouple the lightchains in a total immunoglobulin sample from the heavy chainimmunoglobulins. Decoupling can be achieved by treating the totalimmunoglobulins with a reducing agent, such as DTT (2,3dihydroxybutane-1,4-dithiol), DTE (2,3 dihydroxybutane-1,4-dithiol),thioglycolate, cysteine, sulfites, bisulfites, sulfides, bisulfides,TCEP (tris(2-carboxyethyl)phosphine), 2-mercaptoethanol, and salt formsthereof. In some embodiments, the reducing step is performed at elevatedtemperature, e.g., in a range from about 30° C. to about 65° C., such asabout 55° C., in order to denature the proteins. In some embodiments,the sample is further treated, e.g., by modifying the pH of the sampleor buffering the sample. In some embodiments, the sample can beacidified. In some embodiments, the sample can be neutralized (e.g., bythe addition of a base such as bicarbonate).

Mass Spectrometry Methods

After sample preparation, an immunoglobulin sample, such as a decoupledsample having one or more heavy or light immunoglobulin chains, can besubjected to a mass spectrometry (MS) technique, either directly orafter separation on a high performance liquid chromatography column(HPLC). In some embodiments, liquid chromatography mass spectrometry(LC-MS) can be used to analyze the mass spectrum of the ions. Forexample, the method can be used to identify multiply charged ions (e.g.,the +1 ions, +2 ions, +3 ions, +4 ions, +5 ions, +6 ions, +7 ions, +8ions, +9 ions, +10 ions, +11 ions, +12 ions, +13 ions, +14 ions, +15ions, +16 ions, +17 ions, +18 ions, +19 ions, +20 ions, +21 ions, and+22 ions), resulting from the heavy or light chains in the sample. Insome embodiments, the +11 charged ion is identified and used for furtheranalysis. In some embodiments, the samples are not fragmented during themass spectrometry technique. LC-MS is an analytical technique thatcombines the physical separation capabilities of liquid chromatographywith the mass analysis capabilities of mass spectrometry, and issuitable for detection and potential identification of chemicals in acomplex mixture. Any LC-MS instrument can be used, e.g., the ABSciex5600 Mass Spectrometer. In some embodiments, microflowLC-MS can beutilized. Any suitable microflow instrument can be used, e.g., theEksigent Ekspert 200 microLC. The ion mass spectrum can be analyzed forone or more peaks corresponding to one or more heavy or light chains inthe sample. For example, one or more ion peaks, e.g., a +11 ion peak foreach of the kappa and lambda light chains, can be examined to determinethe ratio of each chain in the sample. In some embodiments, the ratio isdetermined by the peak area of the selected ion peak(s).

In some embodiments, electrospray ionization coupled to a quadrupoletime-of-flight mass spectrometry (ESI-Q-TOF MS) can be used to analyzethe mass spectrum of an immunoglobulin sample, e.g., the mass spectrumof the +11 charge state of the heavy and/or light chains in the sample.Electrospray ionization mass spectrometry (ESI MS) is a useful techniquefor producing ions from macromolecules because it overcomes thepropensity of these molecules to fragment when ionized. In addition, ESIoften produces multiply charged ions, effectively extending the massrange of the analyzer to accommodate the orders of magnitude observed inproteins and other biological molecules. A quadrupole mass analyzer (Q)consists of four cylindrical rods, set parallel to each other. In aquadrupole mass spectrometer, the quadrupole is the component of theinstrument responsible for filtering sample ions based on theirmass-to-charge ratio (m/z). The time-of-flight (TOF) analyzer uses anelectric field to accelerate the ions through the same potential, andthen measures the time they take to reach the detector. If the particlesall have the same charge, the kinetic energies are identical, and theirvelocities depend only on their masses. Lighter ions reach the detectorfirst. Any ESI-Q-TOF mass spectrometer can be used, e.g., the ABSciexTripleTOF 5600 quadrupole time-of-flight mass spectrometer. The massspectrum, e.g., the mass spectrum of multiply charged intact light chainor heavy chain polypeptide ions, can be analyzed to identify one or morepeaks at an appropriate mass/charge expected for the chain. For example,for the light chains, the peaks can occur at about 600-2500 m/z. In someembodiments, the peaks can occur at about 1000-2300 m/z (e.g., about2000-2200 m/z for the +11 ion). Fragment ion peaks can be detected at arange of m/z of 250-2000. In the case of the heavy chains, the peaks canoccur at about 600-2500 m/z. In some embodiments, the peaks can occur atabout 900-2000 m/z.

In some embodiments, electrospray ionization coupled to a quadrupole,time-of-flight orbitrap mass analyzer can be used to analyze the massspectrum of an immunoglobulin sample, e.g., the mass spectrum of the +11charge state of the heavy and/or light chains in the sample

The multiply charged ion peaks can be converted to a molecular massusing known techniques. For example, multiply charged ion peak centroidscan be used to calculate average molecular mass and the peak area valueused for quantification is supplied by a software package. Specifically,multiple ion deconvolution can be performed using the Bayesian ProteinReconstruct software package in the BioAnalyst companion softwarepackage in ABSCIEX Analyst TF 1.6. The following settings can be used:Start mass (Da)=22,000, Stop mass (Da)=26,000 Da, Step mass (Da)=1, S/Nthreshold=20, Minimum intensity %=0, Iterations=20, Adduct: Hydrogen. Alimited mass range was used with a Start m/z=1,100 and a Stop m/z=2,500.Deconvoluted and multiply charged ions can also be manually integratedusing the Manual Integration 33 script in Analyst TF. Providing themolecular mass for the heavy and/or light immunoglobulin chains in thesample facilitates quantification and isotyping of the chains in thesample. For example, the methods provided herein can be used todetermine the ratio of the kappa and lambda light chains in the sample.The kappa/lambda ratio is simply the calculated peak area for the kappalight chain molecular mass distribution divided by the lambda lightchain molecular mass distribution. In addition, the methods providedherein can be used to compare the relative abundance of each of thelight chains as compared to a control or reference sample. As will bediscussed in more detail below, the accepted ratio of kappa to lambdalight chains in a normal serum sample is 3.20. Deviations from thisratio can be indicative of various disorders and therefore is a usefultool for diagnosing and monitoring patients with such disorders.

In some embodiments, matrix assisted laser adsorption ionization-time offlight mass spectrometry (MALDI-TOF MS) can be used to analyze the massspectrum of an immunoglobulin sample. MALDI-TOF MS identifies proteinsand peptides as mass charge (m/z) spectral peaks. Further, the inherentresolution of MALDI-TOF MS allows assays to be devised using multipleaffinity ligands to selectively purify/concentrate and then analyzemultiple proteins in a single assay.

Methods for Screening Biological Samples and for Diagnosing andMonitoring Disorders

The mass spectrometry based methods provided herein can be used todetermine the ratio of the kappa and lambda immunoglobulin light chainsin a sample. In some embodiments, a sample (e.g., a biological sample)having one or more immunoglobulins can be subjected to a massspectrometry assay. The sample can be pretreated to isolate or enrichimmunoglobulins present in the sample and in some cases; theimmunoglobulin light chains can be decoupled from the immunoglobulinheavy chains prior to the mass spectrometry analysis. The spectrumobtained from the assay can then be used to determine the ratio of thekappa and lambda immunoglobulin light chains in the sample. In someembodiments, the relative abundance of the kappa and lambda light chainscan be determined by converting the peak areas of one or more of theidentified peaks into a molecular mass.

The ratios and relative abundance of the immunoglobulin light chains canbe compared to a reference value or a control sample to aid in thediagnosis of various disorders, including polyclonal gammopathies (e.g.,hypergammaglobulinemia), autoimmune disorders (e.g., Sjögren'ssyndrome), infectious disorders (e.g., HIV) and inflammatory disorders(e.g., chronic inflammatory disorders). In such disorders, the ratio ofkappa to lambda immunoglobulin light chains is skewed from the acceptednormal ratio (e.g., a ratio of 3.20). For example, in the case of anautoimmune disorder such as Sjögren's syndrome, the prevalence of kappaimmunoglobulin light chains is increased from normal and the ratio ofkappa to lambda light chains is higher than the normal 3.20, forexample, the ratio can be about 5 (e.g., 83:17). For an inflammatorydisorder such as a chronic inflammatory disorder, the relative abundanceof each of the light chains can be reversed (i.e. a higher prevalence ofthe lambda light chain as compared to the kappa light chain isobserved). For example, the amount of lambda light chains in a samplefrom a patient suffering from such a disorder can be about 0.5 (e.g.,0.54). In some cases, disorders such as hypergammaglobulinemia can bediagnosed based on the relative abundance of the immunoglobulin lightchains as compared to a reference value or control sample. For example,the relative abundance of the light chains compared to a reference valueaccepted as normal can be at least two standard deviations higher; insome cases, at least 50% greater, at least 75% greater, or at least 100%greater, or at least 2-fold higher, 3-fold higher, or 4-fold, or more.In addition to relative ratios, the detection of immunoglobulin cloneswhich appear in greater quantities than the polyclonal background canaid in the diagnosis of disease state. For example, patients who areresponding to a bacterial infection are known to produce oligoclonalimmunoglobulin response towards that bacterial. Observation of anoligoclonal response can then direct the treatment toward infectiousagents.

In some embodiments, the methods provided herein can be used to confirma diagnosis made by current methods such as protein electrophoresis(PEL) or immunofixation (IF) test. For example, if a negative result isobtained from PEL and/or IF, the present methods can be used as asecondary test to confirm or counter such results. In some embodiments,the diagnosis provided herein can be confirmed using such standardmethods.

The mass spectrometry based methods provided herein can also be used formonitoring the treatment of a disorder in a subject. For example, whenthe subject is diagnosed to have polyclonal gammopathy (e.g.,hyperglobulinemia), the methods provided herein can further be used tomonitor a treatment of polyclonal gammopathy. Such methods includeproviding a first sample of the subject before the treatment and asecond sample of the subject during or after the treatment.Immunoglobulins can be isolated or enriched from the first and secondsamples, and subjected to a mass spectrometry technique. The ratio ofthe kappa and lambda light chains is determined before and after thetreatment and compared. A shift of the ratio toward the accepted normalvalue indicates that the treatment may be effective for the subject;while an increased change or no change in the ratio indicates that thetreatment may be ineffective for the subject.

The techniques provided herein can also be used to differentiate humansamples from those of other mammalian species based on the relativedistribution of the kappa and lambda light chains. Such methods may beuseful for prescreening biological samples used in, for example,anti-doping testing.

In addition, the methods provided herein are useful for identifying theisotype of the heavy and or light chain immunoglobulins. In certaindiseases, such as multiple myeloma, there is an increase in the amountof a monoclonal immunoglobulin in the bloodstream. If high levels of themonoclonal immunoglobulin are detected, additional tests are performedto determine the isotypes of the heavy and light chains of themonoclonal immunoglobulin. Current methods use anti-constant regionantibodies to determine the isotype. The methods provided herein providean alternative to current methods and show superior speed, sensitivity,resolution, and robustness than the conventional laboratory tests.

In some embodiments, the methods provided herein can be used to diagnoseinflammatory diseases of the central nervous system (CNS). Examples ofCNS inflammatory diseases that may be diagnosed using methods providedherein include multiple sclerosis, neuromyelitus optica,neurosarcoidosis, subacute sclerosing panencephalitis, andGuillian-Barrre Syndrome. The methods provided herein can be used todetect immunoglobulins located with the cerebral spinal fluid (CSF) of asubject (e.g., a patient). In some embodiments, the method includes (a)providing a cerebral spinal fluid (CSF) sample comprising one or moreimmunoglobulins; (b) subjecting the CSF sample to a mass spectrometrytechnique to obtain a mass spectrum of the CSF sample; and (c)identifying a mass peak corresponding to one or more light chains in theCSF sample.

Prior to subjecting the CSF sample to a mass spectrometry technique toobtain a mass spectrum of the CSF sample, the CSF sample can be dilutedwith a solution (e.g., buffer). For example, the CSF sample can bediluted to about 1:5, 1:3, 1:1, 3:1, or about 5:1 with buffer or othersolution. In some embodiments, the CSF sample is diluted to about 1:1with buffer or other solution. Further, prior to subjecting the serumsample to a mass spectrometry technique the immunoglobulins in the serumcan be enriched with a Melon gel as described previously.

EXAMPLES General Methods. Serum and Immunoglobulin Reagents:

Serum was collected from waste samples obtained from the clinicallaboratory. Purified IgG kappa and IgG lambda from normal donors waspurchased from Bethyl Laboratories (Montgomery, Tex.).

Reagents:

Ammonium bicarbonate, dithiothreitol (DTT), and formic acid werepurchased from Sigma-Aldrich (St. Louis, Mo.). Melon Gel was purchasedfrom Thermo-Fisher Scientific (Waltham Mass.). Water, acetonitrile, and2-propanol were purchased from Honeywell Burdick and Jackson (Muskegon,Mich.).

Serum:

A volume of 50 μL of serum was enriched for immunoglobulins using MelonGel following the manufacturer's instructions. After immunoglobulinenrichment, 25 μL of sample was reduced by adding 25 μL of 100 mM DTTand 25 μL of 50 mM ammonium bicarbonate then incubated at 55° C. for 15minutes before injection. Samples were placed into 96 deep-well PCRplates (300 μL volume) at 9° C. while waiting for injection.

LC Conditions:

An Eksigent Ekspert 200 microLC (Dublin, Calif.) was used forseparation; mobile phase A was water+0.1% formic acid (FA), and mobilephase B was 90% acetonitrile+10% 2-propanol+0.1% FA. A 2 μL injectionwas made onto a 1.0×75 mm Poroshell 300SB-C3, 5 μm particle size columnflowing at 25 μL/minute while the column was heated at 60° C. A 25minute gradient was started at 80% A/20% B, held for 1 minute, ramped to75% A/25% B over 1 minutes, then ramped to 65% A/35% B over 10 minutes,then ramped to 50% A/50% B over 4 minutes, then ramped to 95% A/5% Bover 2 minutes held for 5 minutes, then ramped to 80% A/20% B over 1minute, then equilibrating at 80% A/20% B for 1 minute.

ESI-Q-TOF MS:

Spectra were collected on an ABSciex TripleTOF 5600 quadrupoletime-of-flight mass spectrometer (ABSciex, Vaughan ON, CA) in ESIpositive mode with a Turbo V dual ion source with an automated calibrantdelivery system (CDS). Source conditions were: IS: 5500, Temp: 500, CUR:45, GS1: 35, GS2: 30, CE: 50±5. TOF MS scans were acquired from m/z600-2500 with an acquisition time of 100 ms. Fragment ion scans wereacquired from m/z 350-2000 with an acquisition time of 100 ms. Theinstrument was calibrated every 5 injections through the CDS usingcalibration solution supplied by the manufacturer.

MS Data Analysis:

Analyst TF v1.6 was used for instrument control. Data were viewed usingAnalyst TF v1.6 and PeakView v1.2.0.3. Multiply charged ion peakcentroids were used to calculate average molecular mass and the peakarea value used for quantification through BioAnalyst software providedwith Analyst TF. Multiple ion deconvolution was performed using thefollowing BioAnalyst specific parameters: mass range of 20,000 Da and28,000 Da, hydrogen adduct, step size of 1, S/N of 20, and 20 iterationsfor light chain molecular mass calculations.

Bioinformatics Data Analysis:

The normal distribution used to model the kappa and lambda light chainmolecular mass profile was generated using kappa and lambda genesequences from the Boston University ALBase. Gene sequences wereuploaded into the IMGT alignment tool V-QUEST (Brochet, X et al. NucleicAcids Res 2008; 36:W503-8) and each sequence was aligned from thevariable (V) region Frame 1 (N-terminus) through the joining (J) regionto the beginning of the constant (C) region. Only gene sequences thatincluded the entire V region through the J region were used (46 kappaand 46 lambda). The gene sequence was then translated into thecorresponding amino acid sequence using the ExPASy Translate tool. Thisamino acid sequence was then converted to average molecular mass usingthe ExPASy Compute pI/Mw tool and then added to the molecular mass ofthe corresponding isotype constant region. Each molecular mass wasplaced into 100 Da width bins and the software package JMP 10.0.0 wasused to produce histograms and to calculate the mean molecular mass andto model the normal distribution of calculated molecular masses.

Example 1—Monitoring Kappa and Lambda Light Chain Repertoires in SerumUsing Mass Spectrometry

The inventors have discovered distinct polyclonal kappa and lambda lightchain molecular mass profiles that can be used to identify and quantifykappa and lambda light chains in biological samples. FIG. 4 shows atotal ion chromatogram obtained from the injection of 2 μL melon gelpurified and DTT reduced normal pooled serum analyzed bymicroLC-ESI-Q-TOF MS and using the methods described above. Thehighlighted area represents the 5.0 to 6.0 minute retention time windowwhere light chains begin to elute from the LC column. FIG. 5 shows themass spectrum obtained by summing the spectra collected over this 1minute window with the charge state of the expected polyclonal kappalight chains shown next to the highlighted vertical line. FIG. 5 alsoshows a close up view of the +11 charge state for the expectedpolyclonal kappa and lambda light chains. FIG. 6 shows the deconvolutedmass spectrum of FIG. 5 transformed to molecular mass and showing thekappa and lambda polyclonal molecular mass profile. The inset to FIG. 6shows the normally distributed molecular mass profile calculated fromthe gene sequence data showing an excellent match to the experimentallyobserved molecular mass profile. The mean molecular mass calculated forthe kappa polyclonal light chains was 23,433 Da while the mean molecularmass for the lambda light chains was 22,819 Da. This translates into adifference of 614 Da, 19 Da (3%) lower than the calculated differencebetween kappa and lambda light chains using the gene sequence data.

Example 2—Confirming Light Chain Isotype Labeling

To confirm that the two molecular mass profiles were indeedrepresentative of the kappa and lambda light chain isotypes,commercially available purified IgG kappa and purified IgG lambdapreparations obtained from pooled normal serum were analyzed bymicroLC-ESI-Q-TOF MS and using the methods described above. FIG. 7 showsthe results comparing the deconvoluted molecular mass profiles fornormal pooled serum (top), IgG kappa purified normal pooled serum(middle), and IgG lambda purified normal pooled serum (bottom). Thefigure clearly shows the absence of the lambda polyclonal molecular massprofile in the IgG kappa purified normal pooled serum and the absence ofthe kappa polyclonal molecular mass profile in the IgG lambda purifiednormal pooled serum. Furthermore, the IgG kappa purified and IgG lambdapurified serum sample isotypes were confirmed using top-down MS asdescribed previously (Barnidge. D R et al. J Proteome Res 2014). Theseobservations support the findings that polyclonal kappa light chains inserum have a molecular mass profile between approximately 23,200 Da and23,800 Da and polyclonal lambda light chains in serum have a molecularmass profile between approximately 22,500 Da and 23,200 Da.

In addition to providing the kappa and lambda light chain molecular massprofile, the microLC-ESI-Q-TOF MS methods provided herein also offer therelative abundance of each isotype from serum enriched forimmunoglobulins and reduced with DTT. In FIG. 6, the calculated peakarea for the kappa light chains was found to be 2.40×10⁵ while the peakarea for the lambda light chains was found to be 7.51×10⁴ resulting in akappa/lambda ratio of 3.20 similar to published findings (Haraldsson, Aet al. Ann Clin Biochem 1991; 28 (Pt 5):461-6).

Example 3—Kappa and Lambda Measurements in Non-Human Mammalian Samples

Additional experiments were performed on serum from four other mammalsto evaluate the differences in kappa/lambda expression ratios. FIG. 8shows the results for pooled serum samples derived from sheep, goats,cows, and horses. These molecular mass profiles illustrate that sheep,goat, cow, and horse have polyclonal immunoglobulin light chainmolecular mass profiles that fall into the lambda mass range. Top-downMS was performed on the sheep serum sample to confirm that the observedmolecular mass profile was indeed a lambda isotype (data not shown). Theobservation that lambda light chains are the predominant isotype in oddand even toed ungulates is in agreement with previously publishedobservations (Arun, S S et al. Zentralbl Veterinarmed A 1996; 43:573-6;Sun Y, et al. J Anim Sci Biotechnol 2012; 3:18; and Butler, J E et alDev Comp Immunol 2009; 33:321-33).

Example 4—Ratios of Kappa and Lambda Light Chains in Patients withVarious Disorders

Serum samples from patients having various disorders were examined usingthe methods described above. Specifically, the light chain profiles ofserum patients with high levels of total serum immunoglobulins oftenreferred to as polyclonal gammopathy or hypergammaglobulinemia weretested. FIG. 9 shows the +11 charge state kappa and lambda light chainions observed from serum taken from a patient withhypergammaglobulinemia (upper trace) compared to a normal control serum(lower trace). The mass spectra were acquired by summing all the spectrafrom the elution time of immunoglobulin light chains (data not shown).Upon comparison, it can be seen that the overall abundance of lightchains is approximately 2-fold higher in the serum from the patient withhypergammaglobulinemia as compared to the serum from the normal control.In addition, the spectra from the hypergammaglobulinemia patientexhibits distinct monoclonal light chains present above the polyclonalbackground resulting in an oligoclonal appearance to the spectrum.

Several other serum samples from patients with hypergammaglobulinemiawere analyzed that showed a skewed kappa/lambda light chain molecularmass ratio. FIG. 10 shows the +11 charge state ions observed from normalcontrol serum (top), a patient with a chronic inflammatory response ofunknown origin (middle), and a patient with Sjögren's syndrome anautoimmune disorder involving the salivary and lacrimal glands (bottom).The profile in the middle from the patient with chronic inflammationshows that the overall abundance of lambda light chains is greater thanthe abundance of kappa light chains. The calculated peak area of thekappa light chains was found to be 4.05×10⁵ while the lambda lightchains was found to be 7.44×10⁵ resulting in a kappa/lambda ratio of0.54 or 35:65, nearly the opposite of the kappa/lambda ratio observed inthe normal control serum. The profile from the patient with Sjögren'ssyndrome shows the predominance of kappa light chains. The calculatedpeak area of the kappa light chains was found to be 1.05×10⁵ while thecalculated peak area for the lambda light chains was found to be2.10×10⁴ resulting in a kappa/lambda ratio of 5 or 83:17.

Example 5—Identifying Light Chains in Samples with a Monoclonal Antibody

Experiments were also performed using normal serum spiked with themonoclonal recombinant therapeutic antibody HUMIRA® (adalimumab) whichhas a kappa light chain and an IgG heavy chain. FIG. 11 shows theresponse observed for the light chain from an LC-MS analysis performedas described above. The top of the figure shows the multiply chargedlight chain ions with the multiply charged HUMIRA kappa light chain ionswith their different charge states highlighted. The bottom of FIG. 11shows the molecular masses found when the multiply charged ions in them/z spectrum are converted to their accurate molecular mass in Daltons(Da). The findings demonstrate that the kappa light chain from HUMIRAspiked into normal serum at 0.01 g/dL (100 mg/L) can be identified abovethe polyclonal background at a molecular mass of 23,407 Da. Thismolecular mass matches the mass of the HUMIRA kappa light chain.

Example 6—Sample from a Patient with a Monoclonal Gammopathy

Experiments were also performed using serum from a patient with a knownlambda monoclonal free light chain and who had also been treated withthe monoclonal recombinant therapeutic antibody REMICADE® (infliximab)which has a kappa light chain and an IgG heavy chain. FIG. 12 shows theresponse observed for the light chains from an LC-MS analysis performedas described above. The top of the figure shows the multiply chargedlight chain ions from the endogenous monoclonal lambda light chain andthe kappa light chain from REMICADE. The bottom of FIG. 12 shows themolecular masses found when the multiply charged ions in the m/zspectrum are converted to their accurate molecular mass in Daltons (Da).The findings demonstrate that the endogenous monoclonal lambda lightchain (22,606 Da) and the kappa light chain from the administeredREMICADE (23,433 Da) are clearly visible above the polyclonalbackground. In addition, the endogenous lambda light chain is locatedwithin the lambda molecular mass distribution while the kappa lightchain from Remicade is within the kappa molecular mass distribution withthe correct molecular mass (24,433 Da).

Example 7—Identifying Heavy Chains in Samples Spiked with a MonoclonalAntibody

Experiments were performed using normal serum spiked with the monoclonalrecombinant therapeutic antibody HUMIRA® (adalimumab) which has a kappalight chain and an IgG heavy chain. FIG. 13 shows the response observedfor the heavy chain from an LC-MS analysis performed as described above.The top of the figure shows the multiply charged heavy chain ions withthe multiply charged HUMIRA heavy chain ions with their different chargestates highlighted. The bottom of FIG. 13 shows the molecular massesfound when the multiply charged ions in the m/z spectrum are convertedto their accurate molecular mass in Daltons (Da). The findingsdemonstrate that the IgG heavy chain from HUMIRA spiked into normalserum at 0.5 g/dL (5 g/L) can be identified above the polyclonalbackground at a molecular mass of 50,636 Da which correlates with themass of the HUMIRA heavy chain with glycosylation. The non-glycosylatedform is also observed at 47,140 Da. The method focuses on identifying amonoclonal immunoglobulin above the polyclonal background so as long asa glycoform associated with the monoclonal immunoglobulin is observedabove the polyclonal background; the method is able to isotype the heavychain by molecular mass.

Example 8

A serum samples from an HIV infected patient was analyzed using a methodas provided herein which demonstrated an oligoclonal immune response(FIG. 15). This type of distribution of clones is not possible bycurrent gel based immunoglobulin characterization.

Example 9

CSF and Serum Samples.

Waste samples were collected from the Clinical Immunology Laboratory OCBassay.

Isoelectric Focusing Gel Electrophoresis Followed by IgG Immunoblotting(IgG IEF) OCB Assay.

Standard operating procedures for performing the IgG IEF OCB assaydeveloped by the Clinical Immunology Laboratory were followed andreagent sets from Helena Laboratories (Beaumont, Tex.) were used.

Reagents.

Ammonium bicarbonate, dithiothreitol (DTT), and formic acid werepurchased from Sigma-Aldrich (St. Louis, Mo.). Melon Gel was purchasedfrom Thermo-Fisher Scientific (Waltham Mass.). Water, acetonitrile, and2-propanol were purchased from Honeywell Burdick and Jackson (Muskegon,Mich.). Kappa and lambda monoclonal light chains purified from humanurine were purchased from Bethyl Laboratories (Montgomery, Tex.).

CSF Preparation for Mass Spectrometry Assay.

A volume of 20 μL of CSF was reduced by adding 20 μL of 200 mM DTTsolubilized in 50 mM ammonium bicarbonate buffer, pH 8.0, then incubatedat 55° C. for 30 minutes. Samples were placed into 96 deep-well PCRplates (300 μL volume) at 9° C. while waiting for injection.

Serum Preparation for Mass Spectrometry Assay.

A volume of 20 μL of serum was enriched for immunoglobulins using 180 μLof Melon Gel and then 20 μL of sample was reduced by adding DTT aspreviously described. See Barnidge D R, Dasari S, Botz C M, et al. UsingMass Spectrometry to Monitor Monoclonal Immunoglobulins in Patients witha Monoclonal Gammopathy. J Proteome Res. 2014 Feb. 11.

Liquid Chromatography.

An Eksigent MicroLC 200 Plus System (Foster City, Calif.) was used toseparate immunoglobulins prior to ionization and detection on an ABSciexTripleTOF 5600 quadrupole time-of-flight mass spectrometer (ABSciex,Vaughan ON, Canada) as previously described. See Barnidge D R, Dasari S,Botz C M, et al. Using Mass Spectrometry to Monitor MonoclonalImmunoglobulins in Patients with a Monoclonal Gammopathy. J ProteomeRes. 2014 Feb. 11.

MS Data Analysis.

Analyst TF v1.6 was used for instrument control. Data were viewed usingAnalyst TF v1.6 and PeakView v1.2. The mass spectra used for analysiswere obtained by summing all mass spectra over the known LC retentiontimes for light chains. The peak centroid of specific charge states m/zvalue was used to assess the abundance of a specific monoclonalimmunoglobulin in CSF and serum as previously described. See, Barnidge DR, Dasari S, Ramirez-Alvarado M, et al. Phenotyping polyclonal kappa andlambda light chain molecular mass distributions in patient serum usingmass spectrometry. J Proteome Res. 2014 Nov. 7; 13(11):5198-205 Accuratemolecular calculations were performed by deconvoluting all multiplecharged ions from the protein using BioAnalyst™.

Results.

FIG. 16 illustrates the steps in the gel based and mass spectrometrybased OCB assays. The gel assay (top of FIG. 16) used IEF gelelectrophoresis (1), followed by passive nitrocellulose blotting (2)anti-IgG antibodies, and secondary antibodies to visualize IgGs (3). Theprocess is manual and takes several hours to complete. The massspectrometry assay uses Melon Gel to enrich serum samples for IgG whileCSF samples are diluted 1:1 (1). Both samples are reduced with DTT priorto analysis by microLC-ESI-Q-TOF MS (3). The entire process isautomatable and takes 1 hour. FIG. 17 shows the miRAMM results formatched CSF and serum acquired from a patient that was negative for OCBby IgG IEF. The figure shows the normally distributed polyclonal kappaand lambda molecular mass distributions for the +11 charge state fromreduced light chains. FIG. 18 shows the miRAMM results for matched CSFand serum from a patient with matching CSF and serum OCB by IgG IEF.Multiple kappa and lambda light chains are observed above the polyclonalbackground in both samples. The large band detected in the kappa lightchain region of the CSF had a calculated molecular mass of 23,529.37 Dawhile the light chain found in the serum had a calculated molecular massof 23,528.75 Da, a difference of 0.62 Da. These findings demonstrate theexceptional specificity of miRAMM for matching “bands” in CSF and serum.The ability of miRAMM for identifying CSF specific clones is shown FIG.19 and FIG. 20. FIG. 19 shows the miRAMM results for matched serum andCSF from a patient with kappa OCB bands unique to CSF by IgG IEF whileFIG. 20 shows the miRAMM results for matched serum and CSF from apatient with lambda OCB bands unique to CSF by IgG IEF. The two figuresclearly demonstrate the presence of multiple clonal light chain peaks inthe CSF sample that are not present in the serum sample.

A cohort of 56 patients was analyzed by miRAMM to compare itsperformance to OCB by IgG IEF. If multiple clonal light chains wereuniquely identified in the CSF with a signal to noise ratio greater than3, the sample was called positive. The cohort contained 24 positive and32 negative IgG IEF OCB results. When the patients were blindly analyzedby miRAMM the same patients were recorded as; 22 positive, 34 negative.The 2 discordant did have apparent clonal light chains in the CSF bymiRAMM but the abundance of these light chains was slightly below theS/N cut-off of 3.

miRAMM can also be used to quantitate immunoglobulins. Purifiedmonoclonal kappa and lambda light chain standards were diluted into anOCB-positive CSF. Dilution series were made using the kappa or lambdalight chain ranging from 1 to 50 μg/mL. The peak areas for the kappa andlambda standards diluted linearly with R2 values of 0.999 and 0.992.Inter- and intra-day precision was calculated using an OCB-positive CSF,and the intra-day precision from 20 replicates was 8.1% while theinter-day precision calculated over 10 days was 12.8%. The mass spectrumin FIG. 21 shows overlaid mass spectra from four differentconcentrations of kappa light chain standard spiked into a CSF sample.The kappa light chain standard peak shown in the green trace is the 12.5μg/mL standard while the blue trace represents the 1.5 μg/mL standard.The change in the abundance of each kappa light chain standard is seennext to the fixed abundance of the patient's own kappa light chains.

Example 10

Methods.

Five hundred fifty six (556) serum samples that had been previouslyanalyzed by routine clinical PEL/IFE testing were evaluated by MADLI-TOFMS (Microflex LT, Bruker Daltonics). Prior to analysis, intactimmunoglobulins were isolated from serum with Capture Select™(Hu)LC-kappa and LC-lambda affinity resin (Life Technologies) andreduced with tris(2-carboxyethyl)phosphine hydrochloride (TCEP-HCl,Thermo Scientific). Purified samples were prepared for MALDI-TOFanalysis using dried droplet method and α-cyano-4-hydroxycinnamic acidas matrix. Mass analysis was performed in positive ion mode withsummation of 500 laser shots.

Results.

For spectral analysis, the ion distribution of the MH+1 and MH+2 chargestates of the light chain were compared to the spectrum of normal serum.Any monoclonal abnormalities were distinguished from the normal pattern.Of the 556 samples assayed, abnormal patterns were identified in 406 of421 samples (96%) that were positive by IFE. Abnormalities were alsonoted in 23 of 126 samples (18%) that were negative by IFE. Of the 9samples that were indeterminate by IFE, abnormalities were noted in 2.

Example 11

Mass spectra were generated by analyzing proteins eluted from singledomain antibody fragments with affinity for different immunoglobulinisotypes. Briefly, the mass spectra used to derive the isotype specificm/z distributions for each isotype were generated from 43 healthy adultserum samples. Samples were diluted 10-fold with 1×PBS (100 μL patientsample+900 μL of 1×PBS). 10 μL of each single-domain antibody fragment(targeting the IgG, IgA, IgM, kappa and lambda constant region) coupledto agarose beads (50% beads+50% 1×PBS) were added to 200 μL of thedilute sample and incubated for 30 minutes at RT. The supernatant wasremoved from the beads. The beads were then washed two times in 200 μLof 1×PBS and then two times in 200 μL of water. Then 80 μL of 5% AceticAcid with 50 mMTCEP was added to the beads and incubated for 5 minutesat RT. Then 0.6 μL of supernatant was spotted on each well on a 96-wellMALDI plate which was spotted with 0.6 μL of matrix(α-cyano-4-hydroxycinnamic acid). Subsequently, another 0.6 μL of matrixis spotted on top of the sample. Mass analysis is performed in positiveion mode with summation of 500 laser shots using a MALDI-TOF massspectrometer. A mass/charge (m/z) range of 9,000 to 32,000 m/z isacquired. Next, the mass spectrum generated for each SDAF was overlaidand M-proteins were detected and isotyped by the presence of distinctpeaks with specific m/z regions occupied by the light chain and heavychain repertoire.

OTHER EMBODIMENTS

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

What is claimed is:
 1. A method for detecting immunoglobulin heavychains in a sample, the method comprising: a) providing a biologicalsample comprising immunoglobulins, paired immunoglobulin heavy and lightchains, or mixtures thereof; b) immunopurifying the sample, wherein theimmunopurifying comprises using an antibody selected from the groupconsisting of an anti-human IgG antibody, an anti-human IgA antibody, ananti-human IgM antibody, an anti-human IgD antibody, an anti-human IgEantibody, and combinations thereof; c) subjecting the immunopurifiedsample to a decoupling step wherein immunoglobulin light chains aredecoupled from immunoglobulin heavy chains; and d) subjecting thedecoupled sample to a mass spectrometry technique to obtain a massspectrum of the sample, said mass spectrum comprising one or more peakscorresponding to one or more intact immunoglobulin heavy chains in thesample; wherein said one or more peaks quantify the amount of the one ormore intact immunoglobulin heavy chains in the sample.
 2. The method ofclaim 1, wherein the antibody is a non-human antibody.
 3. The method ofclaim 2, wherein the non-human antibody is at least one of a camelidantibody, a cartilaginous fish antibody, llama, sheep, goat, or a mouseantibody.
 4. The method of claim 3, wherein the antibody is a singledomain antibody fragment (SDAF).
 5. The method of claim 4, wherein theSDAF is derived from a camelid antibody, a cartilaginous fish antibody,llama, a mouse antibody, sheep, goat, or a human antibody.
 6. The methodof claim 5, wherein the SDAF is selected such that the mass spectrumgenerated in step c) for the single domain antibody fragment does notoverlap with the mass spectrum generated in step c) for theimmunoglobulin light chain or immunoglobulin heavy chain.
 7. The methodof claim 6, wherein the SDAF is selected such that the SDAF generates asignal of about 12,500 to about 15,000 m/z in step c) with a singlecharge.
 8. The method of claim 1, wherein the sample comprisingimmunoglobulin light chains, immunoglobulin heavy chains, or mixturesthereof is analyzed as a single fraction in a single analysis.
 9. Themethod claim 1, further comprising determining the pairing ofimmunoglobulin heavy chains and immunoglobulin light chains in thesample.
 10. The method of claim 1, further comprising determining thequantitative amount of one or more of the immunoglobulin heavy chains inthe sample.
 11. The method claim 1, further comprising identifying aM-protein in the sample.
 12. The method of claim 11, further comprisingquantifying the M-protein in the sample.
 13. The method of claim 12,further comprising determining the pairing of immunoglobulin heavychains and immunoglobulin light chains in the M-protein in the sample.14. A method for detecting immunoglobulin heavy chains in a sample, themethod comprising: a) providing a biological sample comprisingimmunoglobulins, paired immunoglobulin heavy and light chains, ormixtures thereof, b) immunopurifying the sample utilizing a singledomain antibody fragment (SDAF) having affinity for an immunoglobulin,wherein said SDAF is selected from the group consisting of an anti-humanIgG SDAF, an anti-human IgA SDAF, an anti-human IgM SDAF, an anti-humanIgD SDAF, an anti-human IgE SDAF, an anti-human kappa SDAF, ananti-human lambda SDAF, and combinations thereof; c) subjecting theimmunopurified sample to a decoupling step where light chainimmunoglobulins are decoupled from the heavy chain immunoglobulins;wherein one or more of the immunoglobulin light chains or immunoglobulinheavy chains is derived from an M-protein; d) subjecting theimmunopurified sample to a mass spectrometry technique to obtain a massspectrum of the sample, said mass spectrum comprising one or more peakscorresponding to one or more intact immunoglobulin light chains in thesample; wherein said one or more peaks quantify the amount of the one ormore intact immunoglobulin heavy chains in the sample, wherein the massspectrometry technique is chosen from the group consisting of (i) liquidchromatography electrospray ionization coupled to mass analyzer (ii) amicroflow liquid chromatography electrospray ionization coupled to aquadrupole time-of-flight mass spectrometry technique and (iii) a matrixassisted laser adsorption ionization-time of flight mass spectrometrytechnique; and e) determining one or more of (i) the identity of theM-protein, (ii) the quantity of the M-protein, (iii) the pairing ofimmunoglobulin heavy chains and immunoglobulin light chains of theM-protein, and (iv) the quantitative amount of one or more of theimmunoglobulin heavy chains and M-protein in the sample.
 15. The methodof claim 14, wherein the SDAF is derived from a camelid antibody, acartilaginous fish antibody, llama, a mouse antibody, sheep, goat, or ahuman antibody.
 16. The method of claim 15, wherein the SDAF is selectedsuch that the mass spectrum generated in step d) for the SDAF does notoverlap with the mass spectrum generated in step d) for theimmunoglobulin light chain or immunoglobulin heavy chain.
 17. The methodof claim 16, wherein the SDAF is selected such that the SDAF generates asignal of about 12,500 to about 15,000 m/z in step d) with a singlecharge.
 18. A method for monitoring treatment of a disorder in asubject, said method comprising: a) providing a biological sampleobtained from the subject, wherein the biological sample comprisesimmunoglobulins, paired immunoglobulin heavy and light chains, ormixtures thereof; b) immunopurifying the sample, wherein theimmunopurifying comprises using an antibody selected from the groupconsisting of an anti-human IgG antibody, an anti-human IgA antibody, ananti-human IgM antibody, an anti-human IgD antibody, an anti-human IgEantibody, and combinations thereof; c) subjecting the immunopurifiedsample to a decoupling step wherein immunoglobulin light chains aredecoupled from immunoglobulin heavy chains; and d) subjecting thedecoupled sample to a mass spectrometry technique to obtain a massspectrum of the sample, said mass spectrum comprising one or more peakscorresponding to one or more intact immunoglobulin heavy chains or oneor more intact immunoglobulin light chains in the sample; wherein saidone or more peaks quantify the amount of the one or more intactimmunoglobulin heavy chains or one or more intact immunoglobulin lightchains in the sample.
 19. The method of claim 18, wherein the treatmentcomprises administering a therapeutic monoclonal antibody to thesubject, and wherein said one or more peaks that quantify the amount ofthe one or more intact immunoglobulin heavy chains or one or more intactimmunoglobulin light chains are from said therapeutic monoclonalantibody.
 20. The method of claim 18, wherein said biological sample isselected from the group consisting of a whole blood sample, a serumsample, a plasma sample, a urine sample, and a cerebrospinal fluidsample.